django/docs/ref/models/class.txt

=====================
Model class reference
=====================

.. currentmodule:: django.db.models

This document covers features of the :class:`~django.db.models.Model` class.
For more information about models, see :doc:`the complete list of Model
reference guides </ref/models/index>`.

Attributes
==========

``DoesNotExist``
----------------

.. exception:: Model.DoesNotExist

    This exception is raised by the ORM when an expected object is not found.
    For example, :meth:`.QuerySet.get` will raise it when no object is found
    for the given lookups.

    Django provides a ``DoesNotExist`` exception as an attribute of each model
    class to identify the class of object that could not be found, allowing you
    to catch exceptions for a particular model class. The exception is a
    subclass of :exc:`django.core.exceptions.ObjectDoesNotExist`.

``MultipleObjectsReturned``
---------------------------

.. exception:: Model.MultipleObjectsReturned

    This exception is raised by :meth:`.QuerySet.get` when multiple objects are
    found for the given lookups.

    Django provides a ``MultipleObjectsReturned`` exception as an attribute of
    each model class to identify the class of object for which multiple objects
    were found, allowing you to catch exceptions for a particular model class.
    The exception is a subclass of
    :exc:`django.core.exceptions.MultipleObjectsReturned`.

``NotUpdated``
--------------

.. versionadded:: 6.0

.. exception:: Model.NotUpdated

    This exception is raised when :ref:`a forced update
    <ref-models-force-insert>` of a :class:`~django.db.models.Model` instance
    does not affect any rows.

    Django provides a ``NotUpdated`` exception as an attribute of each model
    class to identify the class of object that could not be updated, allowing
    you to catch exceptions for a particular model class. The exception is a
    subclass of :exc:`django.core.exceptions.ObjectNotUpdated` and inherits
    from :exc:`django.db.DatabaseError` for backward compatibility reasons.

``objects``
-----------

.. attribute:: Model.objects

    Each non-abstract :class:`~django.db.models.Model` class must have a
    :class:`~django.db.models.Manager` instance added to it.
    Django ensures that in your model class you have  at least a
    default ``Manager`` specified. If you don't add your own ``Manager``,
    Django will add an attribute ``objects`` containing default
    :class:`~django.db.models.Manager` instance. If you add your own
    :class:`~django.db.models.Manager` instance attribute, the default one does
    not appear. Consider the following example::

        from django.db import models


        class Person(models.Model):
            # Add manager with another name
            people = models.Manager()

    For more details on model managers see :doc:`Managers </topics/db/managers>`
    and :ref:`Retrieving objects <retrieving-objects>`.